%%%-------------------------------------------------------------------
%%% @author Administrator
%%% @copyright (C) 2019, <COMPANY>
%%% @doc
%%%
%%% @end
%%% Created : 17. 10月 2019 10:35
%%%-------------------------------------------------------------------
-module(reload).
-author("Administrator").

-behaviour(gen_server).

%% API
-export([start_link/0]).

%% gen_server callbacks
-export([init/1,
  handle_call/3,
  handle_cast/2,
  handle_info/2,
  terminate/2,
  code_change/3]).

-include_lib("kernel/include/file.hrl").
-include("include/logger.hrl").
-define(SERVER, ?MODULE).

-record(state, {last, tref}).

%%%===================================================================
%%% API
%%%===================================================================

%%--------------------------------------------------------------------
%% @doc
%% Starts the server
%%
%% @end
%%--------------------------------------------------------------------
-spec(start_link() ->
  {ok, Pid :: pid()} | ignore | {error, Reason :: term()}).
start_link() ->
  gen_server:start_link({local, ?SERVER}, ?MODULE, [], []).

%%%===================================================================
%%% gen_server callbacks
%%%===================================================================

%%--------------------------------------------------------------------
%% @private
%% @doc
%% Initializes the server
%%
%% @spec init(Args) -> {ok, State} |
%%                     {ok, State, Timeout} |
%%                     ignore |
%%                     {stop, Reason}
%% @end
%%--------------------------------------------------------------------
-spec(init(Args :: term()) ->
  {ok, State :: #state{}} | {ok, State :: #state{}, timeout() | hibernate} |
  {stop, Reason :: term()} | ignore).
init([]) ->
  {ok, TRef} = timer:send_interval(timer:seconds(1), doit),
  {ok, #state{last = erlang:localtime(), tref = TRef}}.

%%--------------------------------------------------------------------
%% @private
%% @doc
%% Handling call messages
%%
%% @end
%%--------------------------------------------------------------------
-spec(handle_call(Request :: term(), From :: {pid(), Tag :: term()},
    State :: #state{}) ->
  {reply, Reply :: term(), NewState :: #state{}} |
  {reply, Reply :: term(), NewState :: #state{}, timeout() | hibernate} |
  {noreply, NewState :: #state{}} |
  {noreply, NewState :: #state{}, timeout() | hibernate} |
  {stop, Reason :: term(), Reply :: term(), NewState :: #state{}} |
  {stop, Reason :: term(), NewState :: #state{}}).
handle_call(_Request, _From, State) ->
  {reply, ok, State}.

%%--------------------------------------------------------------------
%% @private
%% @doc
%% Handling cast messages
%%
%% @end
%%--------------------------------------------------------------------
-spec(handle_cast(Request :: term(), State :: #state{}) ->
  {noreply, NewState :: #state{}} |
  {noreply, NewState :: #state{}, timeout() | hibernate} |
  {stop, Reason :: term(), NewState :: #state{}}).
handle_cast(_Request, State) ->
  {noreply, State}.

%%--------------------------------------------------------------------
%% @private
%% @doc
%% Handling all non call/cast messages
%%
%% @spec handle_info(Info, State) -> {noreply, State} |
%%                                   {noreply, State, Timeout} |
%%                                   {stop, Reason, State}
%% @end
%%--------------------------------------------------------------------
-spec(handle_info(Info :: timeout() | term(), State :: #state{}) ->
  {noreply, NewState :: #state{}} |
  {noreply, NewState :: #state{}, timeout() | hibernate} |
  {stop, Reason :: term(), NewState :: #state{}}).

handle_info(doit, State) ->
  Now = erlang:localtime(),
  Last =
    case State#state.last of
      undefined -> 0;
      _LL -> _LL
    end,
  check_code(Last, Now),
  {noreply, State#state{last = Now}};

handle_info(_Info, State) ->
  {noreply, State}.




%%--------------------------------------------------------------------
%% @private
%% @doc
%% This function is called by a gen_server when it is about to
%% terminate. It should be the opposite of Module:init/1 and do any
%% necessary cleaning up. When it returns, the gen_server terminates
%% with Reason. The return value is ignored.
%%
%% @spec terminate(Reason, State) -> void()
%% @end
%%--------------------------------------------------------------------
-spec(terminate(Reason :: (normal | shutdown | {shutdown, term()} | term()),
    State :: #state{}) -> term()).
terminate(_Reason, _State) ->
  ok.

%%--------------------------------------------------------------------
%% @private
%% @doc
%% Convert process state when code is changed
%%
%% @spec code_change(OldVsn, State, Extra) -> {ok, NewState}
%% @end
%%--------------------------------------------------------------------
-spec(code_change(OldVsn :: term() | {down, term()}, State :: #state{},
    Extra :: term()) ->
  {ok, NewState :: #state{}} | {error, Reason :: term()}).
code_change(_OldVsn, State, _Extra) ->
  {ok, State}.

%%%===================================================================
%%% Internal functions
%%%===================================================================

%%热更代码
check_code(From, To) ->
  [case file:read_file_info(Filename) of
     {ok, #file_info{mtime = Mtime}} when Mtime >= From, Mtime < To ->
       reload(Module);
     {ok, _} ->
       unmodified;
     {error, enoent} ->
       gone;
     {error,enotdir} ->
       gone;
     {error, Reason} ->
       ?INFO("Error reading ~s's file info: ~p~n",
         [Filename, Reason]),
       error
   end || {Module, Filename} <- code:all_loaded(), is_list(Filename)].

reload(tcp_reader) ->
  ok;
reload(tcp_listener) ->
  ok;
reload(tcp_accepter) ->
  ok;
reload(Module) ->
  ?INFO("Reloading ~p ...\n", [Module]),
  code:purge(Module),
  case code:load_file(Module) of
    {module, Module} -> reload;
    {error, _} -> error
  end.


